JP2008143314A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for heavy load capable of effectively reducing rolling resistance and maintaining superior fuel efficiency from an initial stage to a terminal stage of the tire service life. <P>SOLUTION: The pneumatic tire for heavy load is provided with stiffeners 7 comprising hard stiffeners 7a adjacent to outer sides in the tire radial direction of bead cores 6 embedded inside bead parts 1, respectively and soft stiffeners 7b adjacent to the outer sides in the tire radial direction of the hard stiffeners 7a. In this case, the storage elastic modulus E' of the hard stiffener 7a is set to be 30 MPa or more and the loss tangent tanδ of the hard stiffener 7a is set to be 0.25 or less. The loss tangent tanδ of a side rubber 8 positioned on the outer side in the tire width direction of a carcass 4 of a side part 2 is set to be 0.11 or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heavy-duty pneumatic tire, and more particularly to a heavy-duty pneumatic tire capable of maintaining good fuel economy from the beginning to the end of the tire life.

  In recent years, there is a demand for reducing the rolling resistance of heavy duty pneumatic tires and improving the fuel efficiency of the tires. On the other hand, the initial rolling resistance of the tire can be reduced by reducing the hysteresis loss of the tread rubber used in the tread portion. However, in this case, with the wear of the tread rubber, there is a problem that the effect of reducing rolling resistance is reduced.

  On the other hand, suppressing deformation of the tire case member and reducing the hysteresis loss are effective in reducing good rolling resistance from the beginning to the end of the tire life. For example, in JP-A-7-61214 (Patent Document 1), JP-A-5-254308 (Patent Document 2) and JP-A-5-254310 (Patent Document 3), the tan δ of the side rubber is 0.02 to 0.15. As a result, a tire achieving low fuel consumption is disclosed.

JP-A-7-61214 JP-A-5-254308 JP-A-5-254310

  However, as a result of studies by the present inventor, when the single member is changed, the strain distribution cannot be maximized by changing the strain distribution, and there is still room for improvement in the rolling resistance reduction effect. I understood that.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, the rolling resistance is effectively reduced, and a heavy load capable of maintaining excellent fuel efficiency from the beginning to the end of the tire life. It is to provide a heavy duty pneumatic tire.

  As a result of intensive studies to achieve the above object, the inventor of the present invention, in a heavy duty pneumatic tire having a stiffener composed of a hard stiffener and a soft stiffener on the outer side in the tire radial direction of the bead core, E ') is set to 30MPa or more to suppress the deformation of the bead portion, to reduce the energy loss of the bead portion, and considering that the deformation of the side portion increases as the deformation of the bead portion is suppressed. The loss tangent (tan δ) of the side rubber disposed on the side portion is set to 0.11 or less, and the energy loss of the side portion is reduced, and the rolling resistance of the tire can be greatly reduced by the synergistic effect of both, and the present invention is It came to complete.

That is, the heavy duty pneumatic tire of the present invention has a pair of bead portions and a pair of side portions, and a tread portion connected to both side portions, and extends in a toroidal shape between the pair of bead portions, A carcass that reinforces each of these parts, and a stiffener disposed outside the bead core in the tire radial direction of each bead core embedded in the bead part, and the stiffener adjacent to the outer side of the bead core in the tire radial direction and the tire of the hard stiffener Consisting of a soft stiffener adjacent to the outside in the radial direction,
The storage modulus (E ′) of the hard stiffener is 30 MPa or more and the loss tangent (tan δ) is 0.25 or less,
The loss tangent (tan δ) of the side rubber located on the outer side in the tire width direction of the carcass of the side portion is 0.11 or less.

  In a preferred example of the heavy-duty pneumatic tire of the present invention, the side rubber has a filler of 30 to 60 mass composed of carbon black and / or silica with respect to 100 mass parts of a rubber component composed of diene rubber containing at least natural rubber. A rubber composition obtained by blending parts is used. Here, the rubber component of the rubber composition used for the side rubber preferably includes a modified polybutadiene rubber having a nitrogen-containing functional group. The nitrogen-containing functional group is preferably derived from hexamethyleneimine.

  In another preferred embodiment of the heavy duty pneumatic tire of the present invention, the hard stiffener includes a rubber component composed of a diene rubber, carbon black, a phenolic resin, and a resin curing agent that is a methylene donor, A rubber composition having a carbon black content of 30 to 100 parts by mass and a phenolic resin content of 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component is used.

  According to the present invention, the energy loss of the bead part and the side part is reduced, and the rolling resistance is effectively reduced by the synergistic effect, and the fuel efficiency is excellent from the beginning to the end of the tire life. It is possible to provide a heavy duty pneumatic tire capable of maintaining the properties.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an embodiment of the heavy duty pneumatic tire of the present invention. The tire shown in FIG. 1 has a pair of bead portions 1 and a pair of side portions 2, and a tread portion 3 connected to both side portions 2, and extends in a toroidal shape between the pair of bead portions 1. A radial carcass 4 that reinforces each of these parts 1, 2, 3, a belt 5 disposed on the outer side in the tire radial direction of the crown part of the carcass 4, and a ring-shaped bead core 6 tire embedded in the bead part 1. And a stiffener 7 disposed on the radially outer side. The stiffener 7 includes a hard stiffener 7a having a relatively high rigidity adjacent to the outer side of the bead core 6 in the tire radial direction and a soft stiffener 7b having a relatively low rigidity adjacent to the outer side of the hard stiffener 7a in the tire radial direction. Further, a side rubber 8 is disposed on the outer side in the tire width direction of the carcass 4 of the side portion 2.

  In the illustrated tire, the radial carcass 4 includes a main body portion 4a extending toroidally between the bead cores 6 and a folded portion 4b wound around the bead cores 6 radially outward from the inner side to the outer side in the tire width direction. And have. The structure and the number of plies of the radial carcass 4 are not limited to this. And the stiffener 7 is arrange | positioned between the main-body part 4a of the radial carcass 4, and the folding | returning part 4b.

  Here, in the heavy duty pneumatic tire of the present invention, the storage modulus (E ′) of the hard stiffener 7a is 30 MPa or more and the loss tangent (tan δ) is 0.25 or less, and the loss tangent ( tanδ) is 0.11 or less. By setting the storage elastic modulus (E ′) of the hard stiffener 7a to 30 MPa or more, the deformation of the bead part 1 can be suppressed and the energy loss of the bead part 1 can be reduced. If the deformation of the bead part 1 is suppressed, the deformation of the side part 2 increases. However, in the heavy duty pneumatic tire of the present invention, the loss tangent (tan δ) of the side rubber 8 disposed on the side part 2 is 0.11 or less. Therefore, the energy loss of the side part 2 can also be reduced. Moreover, the rolling resistance of the tire is greatly reduced by the synergistic effect of the energy loss reducing effect of the bead portion 1 and the energy loss reducing effect of the side portion 2.

  In addition, if the storage elastic modulus (E ') of the said hard stiffener 7a is less than 30 MPa, the deformation | transformation inhibitory effect of the bead part 1 is inadequate. If the loss tangent (tan δ) of the hard stiffener 7a exceeds 0.25, the energy loss of the hard stiffener 7a increases and the energy loss of the bead portion 1 cannot be sufficiently reduced. Here, from the viewpoint of improving the effect of suppressing deformation of the bead portion 1, the storage elastic modulus (E ′) of the hard stiffener 7a is preferably 35 MPa or more. From the viewpoint of further reducing the energy loss of the hard stiffener 7a, the loss tangent (tan δ) of the hard stiffener 7a is preferably 0.22 or less.

  If the loss tangent (tan δ) of the side rubber 8 exceeds 0.11, the effect of reducing the energy loss of the side portion 2 is insufficient. From the viewpoint of further reducing the energy loss of the side portion 2, the loss tangent (tan δ) of the side rubber 8 is preferably 0.1 or less.

  For the side rubber 8, a rubber composition obtained by blending 30 to 60 parts by mass of a filler made of carbon black and / or silica with 100 parts by mass of a rubber component made of a diene rubber containing at least natural rubber is used. Is preferred. When the blending amount of the filler is less than 30 parts by mass with respect to 100 parts by mass of the rubber component, the rigidity of the side part 2 is insufficient. On the other hand, when it exceeds 60 parts by mass, the energy loss of the side part 2 cannot be sufficiently reduced. There is. Here, examples of the diene rubber to be used include natural rubber (NR) and synthetic diene rubbers such as polybutadiene rubber (BR), polyisoprene rubber (IR), and styrene / butadiene copolymer rubber (SBR). It is done. These rubber components may be used alone or in a blend of two or more. Moreover, there is no restriction | limiting in particular as carbon black and / or silica to be used, Various carbon black and / or silica can be used.

  The rubber component of the rubber composition for the side rubber 8 preferably contains a modified polybutadiene rubber having a nitrogen-containing functional group in addition to natural rubber (NR). The modified polybutadiene rubber can improve the dispersibility of fillers such as carbon black and silica, and has the effect of reducing the loss tangent (tan δ) of the side rubber 8. Here, the content of the natural rubber in the rubber component of the rubber composition for the side rubber 8 is preferably in the range of 60 to 40 parts by mass, and the content of the modified polybutadiene rubber is preferably in the range of 40 to 60 parts by mass.

  The modified polybutadiene rubber has a nitrogen-containing functional group at the active end after polymerizing 1,3-butadiene or synthesizing polybutadiene having an active end using a polymerization initiator having a nitrogen-containing functional group. It can be synthesized by a known method such as modification with a modifying agent. Here, the nitrogen-containing functional group is preferably a functional group derived from hexamethyleneimine (for example, a hexamethyleneimino group). The above-mentioned polymerization initiator having a nitrogen-containing functional group may be preliminarily prepared from a lithium compound such as n-butyllithium and a secondary amine such as hexamethyleneimine and used in the polymerization reaction. You may let them. Examples of the modifying agent include tin-containing compounds such as tin tetrachloride, N, N′-dimethylimidazolidinone, N-methylpyrrolidone, 4-dimethylaminobenzylideneaniline, and 4,4′-bis (N, N-dimethyl). Nitrogen-containing compounds such as amino) benzophenone, silicon tetrachloride, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, N- (1-methylpropylidene) -3- (triethoxysilyl) -1-propanamine, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine, N- (3-triethoxysilylpropyl) -4,5-dihydroimidazole, 3 Examples include silicon-containing compounds such as 3-methacryloyloxypropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, and 3-triethoxysilylpropyl succinic anhydride. That.

  The rubber composition for the side rubber 8 is usually used in the rubber industry such as a vulcanizing agent, a vulcanization accelerator, zinc oxide, stearic acid, an anti-aging agent in addition to the rubber component, carbon black and / or silica described above. The compounding agent can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition for the side rubber 8 is blended with a rubber component containing at least natural rubber, together with carbon black and / or silica, and various compounding agents appropriately selected as necessary, kneaded, heated, extruded. It can manufacture by doing.

  On the other hand, the hard stiffener 7a includes a rubber component made of a diene rubber, carbon black, a phenolic resin, and a resin curing agent that is a methylene donor, and the carbon black is mixed with 100 parts by mass of the rubber component. It is preferable to use a rubber composition having an amount of 30-100 parts by mass and a phenolic resin content of 5-30 parts by mass. When the blending amount of the carbon black is less than 30 parts by mass with respect to 100 parts by mass of the rubber component, the storage elastic modulus (E ′) of the hard stiffener 7a is lowered, and the deformation of the bead part 1 may not be sufficiently suppressed. On the other hand, if it exceeds 100 parts by mass, the energy loss of the hard stiffener 7a may increase, and the energy loss of the bead part 1 may not be sufficiently reduced. Moreover, if the compounding quantity of a phenol-type resin is less than 5 mass parts with respect to 100 mass parts of rubber components, the storage elastic modulus (E ') of the hard stiffener 7a will fall, and the deformation | transformation of the bead part 1 cannot fully be suppressed. On the other hand, if it exceeds 30 parts by mass, the energy loss of the hard stiffener 7a increases, and the energy loss of the bead part 1 may not be sufficiently reduced.

  In the rubber composition for the hard stiffener 7a, natural rubber (NR), polybutadiene rubber (BR), polyisoprene rubber (IR), styrene / butadiene copolymer rubber (SBR), etc. are synthesized as the diene rubber. A diene rubber is mentioned. These rubber components may be used alone or in a blend of two or more.

  Examples of the phenolic resin include novolak-type phenol-formaldehyde condensate, novolac-type cresol-formaldehyde condensate, novolac-type resorcin-formaldehyde condensate, and modified products thereof. Among these, novolac-type phenol-formaldehyde condensate And its modified products are preferred. Here, as the modified product, the condensate is modified with an oil such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid or linolenic acid, or modified with an aromatic hydrocarbon such as xylene or mesitylene. And those modified with rubber such as nitrile rubber. These novolac type phenol resins may be used alone or in a combination of two or more.

  Examples of the curing agent for the resin include methylene donors such as hexamethylenetetramine, hexamethoxymethylmelamine, and paraformaldehyde. Among these, hexamethylenetetramine and hexamethoxymethylmelamine are preferable. These curing agents for resins may be used alone or in combination of two or more. In addition, although the compounding quantity of this hardening | curing agent for resin is not specifically limited, The range of 5-50 mass% of the compounding quantity of the said phenol resin is preferable.

  In the rubber composition for the hard stiffener 7a, in addition to the above-described rubber component, carbon black, phenolic resin, and a curing agent for a resin that is a methylene donor, a vulcanizing agent, a vulcanization accelerator, zinc oxide, stearic acid, A compounding agent usually used in the rubber industry such as an anti-aging agent can be appropriately selected and blended within a range not impairing the object of the present invention. As these compounding agents, commercially available products can be suitably used. In the rubber composition for the hard stiffener 7a, the rubber component is blended with carbon black, phenolic resin, and methylene donor, and various compounding agents appropriately selected as necessary, and kneaded, heated, and extruded. It can manufacture by doing.

  The heavy duty pneumatic tire of the present invention can be manufactured in accordance with a conventional method such that the physical properties of the hard stiffener 7a and the side rubber 8 are in the above-mentioned ranges. In the heavy duty pneumatic tire of the present invention, members other than the hard stiffener 7a and the side rubber 8 are not particularly limited, and known members can be used. In the heavy-duty pneumatic tire of the present invention, as the gas filled in the tire, normal or air with a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A rubber composition having the composition shown in Table 1 and Table 2 was prepared according to a conventional method, and the rubber composition was used for the hard stiffener 7a or the side rubber 8 to have a structure shown in FIG. 1 and a heavy load of 11R22.5. A heavy duty pneumatic tire was produced. The rolling resistance, storage elastic modulus (E ′), and loss tangent (tan δ) of the obtained tire were measured and evaluated by the following methods. The results are shown in Table 3.

(1) Rolling resistance With normal load and internal pressure, rolling resistance after a new article at 80 km / h and after running was measured, and an axial torque relative to the control (tire of Comparative Example 1) was displayed as an index. It shows that rolling resistance is so small that an index value is small. The rolling resistance after running was measured after buffing the tire until the remainder of the main groove depth was 3 mm.

(2) Storage elastic modulus (E ′) and loss tangent (tan δ)
A hard stiffener and side rubber were cut out from the test tire, and the storage modulus (E ′) and loss tangent (tan δ) of the hard stiffener were measured with a spectrometer at a temperature of 25 ° C., a strain of 2%, and a frequency of 52 Hz. Side rubber loss tangent (tan δ) was measured.

* 1 Sumitomo Bakelite, Sumilite Resin PR-50235, Softening point: 121 ° C
* 2 Hexamethoxymethylmelamine, manufactured by AMERICANYANAMID COMPANY, CYREZ964, Alteration start temperature: 120 ° C
* 3 Nt-butyl-2-benzothiazolylsulfenamide

* 4 JSR, BR01
* 5 Modified polybutadiene rubber produced by the following method
* 6 N-Cyclohexyl-2-benzothiazolylsulfenamide

<Production example of modified polybutadiene rubber>
Injecting 283 g of cyclohexane, 50 g of 1,3-butadiene, 0.0057 mmol of 2,2-ditetrahydrofurylpropane, and 0.513 mmol of hexamethyleneimine as cyclohexane solutions into a pressure-resistant glass container with an internal volume of about 900 mL that has been dried and purged with nitrogen. Then, 0.57 mmol of n-butyllithium (BuLi) was added thereto, and polymerization was carried out in a hot water bath at 50 ° C. equipped with a stirrer for 4.5 hours. The polymerization addition rate was almost 100%. To this polymerization system, 0.100 mmol of tin tetrachloride was added as a cyclohexane solution and stirred at 50 ° C. for 30 minutes. Thereafter, 0.5 mL of a 5% solution of 2,6-di-t-butylparacresol (BHT) in isopropanol was added to stop the reaction, followed by drying according to a conventional method to obtain a modified polybutadiene rubber (modified BR). . The amount of vinyl bonds (1,2-bonds) in the obtained modified BR was determined from the integration ratio in the spectrum of ¹ H-NMR [manufactured by JEOL, Alpha 400 MHz NMR apparatus, in CDCl ₃ ]. The amount was 14%. The coupling efficiency of the obtained modified BR was calculated using the area ratio of the high molecular weight peak in the data obtained from gel permeation chromatography (GPC), and the coupling efficiency was 65%. It was. The glass transition temperature was -95 ° C.

  As apparent from the results of the examples in Table 3, the storage elastic modulus (E ′) of the hard stiffener is 30 MPa or more and the loss tangent (tan δ) is 0.25 or less, while the loss tangent (tan δ) of the side rubber is 0.11 or less. Thus, it can be seen that, compared to the tire of Comparative Example 1, the rolling resistance at the time of a new article and after running can be greatly reduced.

  On the other hand, the tire of Comparative Example 2 in which the storage elastic modulus (E ′) of the hard stiffener is less than 30 MPa, and the tires of Comparative Examples 3 and 4 in which the loss tangent (tan δ) of the side rubber exceeds 0.11 are rolling when new and after running. The effect of reducing resistance was smaller than that of the tire of the example.

It is sectional drawing which shows one embodiment of the heavy-duty pneumatic tire of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side part 3 Tread part 4 Radial carcass 4a Carcass main-body part 4b Carcass folding | turning part 5 Belt 6 Bead core 7 Stiffener 7a Hard stiffener 7b Soft stiffener 8 Side rubber

Claims (5)

A carcass having a pair of bead portions and a pair of side portions, and a tread portion connected to both side portions, extending in a toroidal shape between the pair of bead portions, and reinforcing the respective portions; and in the bead portion A stiffener disposed on the radially outer side of the tire of each of the buried bead cores, the stiffener comprising a hard stiffener adjacent to the radially outer side of the bead core and a soft stiffener adjacent to the radially outer side of the rigid stiffener. In heavy duty pneumatic tires,
The storage modulus (E ′) of the hard stiffener is 30 MPa or more and the loss tangent (tan δ) is 0.25 or less,
A heavy duty pneumatic tire characterized in that a loss tangent (tan δ) of a side rubber located on the outer side in the tire width direction of the carcass of the side portion is 0.11 or less.   A rubber composition obtained by blending 30 to 60 parts by mass of a filler composed of carbon black and / or silica with 100 parts by mass of a rubber component composed of a diene rubber containing at least natural rubber in the side rubber is used. The heavy duty pneumatic tire according to claim 1, wherein the pneumatic tire is a heavy duty pneumatic tire.   The heavy duty pneumatic tire according to claim 2, wherein the rubber component of the rubber composition used for the side rubber includes a modified polybutadiene rubber having a nitrogen-containing functional group.   The heavy-duty pneumatic tire according to claim 3, wherein the nitrogen-containing functional group is derived from hexamethyleneimine.   The hard stiffener includes a rubber component composed of a diene rubber, carbon black, a phenolic resin, and a curing agent for resin that is a methylene donor, and the blending amount of carbon black is 30 to 100 parts by mass of the rubber component. The heavy-duty pneumatic tire according to claim 1, wherein the rubber composition is used in an amount of 100 parts by weight and a phenolic resin content of 5 to 30 parts by weight.

Images